Anterior ischemic optic neuropathy (AION) is the most common cause of acute optic nerve disease in men and women aged 50 years or more. It causes painless visual loss, loss of part of the visual field, and swelling of the optic nerve insie the eye. Unfortunately not only does vision rarely recover, but there is no successful treatment, despite 2 medium-sized randomized clinical trials and several small-scale studies. As part of a program to find new ways of treated optic neuropathy, we developed novel drugs that chemically reduce disulfide bonds and protect retinal ganglion cell axons, the fibers that project through the optic nerve from the eye to the brain. These phosphine- borane complexes are effective in rat optic nerve transection and experimental glaucoma. They presumably reduce intra- or intermolecular disulfide bonds in one or more critical target proteins. However, we do not know the identity of the proteins undergoing oxidative disulfide formation in diseases such as AION. If those targets can be identified, they can serve as the basis for making more specific phosphine-borane complexes, which then could be used as novel AION therapeutics. We propose to use a sensitive redox proteomic screen to identify the protein target(s) within the optic nerve that undergo sulfhydryl oxidation after rodent AION, and then use the putative target(s) to synthesize a library of 20-30 potentially more specific phosphine- borane complexes. We then will determine a lead candidate by finding which optimally reduces the critical targets, and test it in the rAION model. This lead phosphine-borane complex could then be a candidate for translation into primate models and eventually clinical trial planning.